Previously Undescribed Antibacterial Polyketides from Heterotrophic Bacillus amyloliquefaciens Associated with Seaweed Padina gymnospora

A heterotrophic marine bacterium Bacillus amyloliquefaciens isolated from seaweed Padina gymnospora exhibited broad spectra of antibacterial activities against pathogenic bacteria Aeromonas hydrophila, Vibrio harveyi, Vibrio vulnificus, and Vibrio parahaemolyticus. The seaweed-associated B. amyloliquefaciens was recognized to possess functional type I polyketide synthase-1 (pks-1) gene, and was used to isolate four homologous compounds with polyketide frameworks. The compounds were characterized as 11-(15-butyl-13-ethyl-tetrahydro-12-oxo-2H-pyran-13-yl) propyl-2-methylbenzoate (1), 9-(tetrahydro-12-isopropyl-11-oxofuran-10-yl)-ethyl-4-ethoxy-2-hydroxybenzoate (2), 12-(aminomethyl)-11-hydroxyhexanyl-10-phenylpropanoate (3), and 7-(14-hydroxypropan-13-yl)-8-isobutyl-7,8-dihydrobenzo[c]oxepin-1(3H)-one (4) by comprehensive nuclear magnetic resonance and mass spectroscopic experiments. The compounds 1-4 displayed significant antibacterial activities against clinically important pathogens V. parahaemolyticus and V. vulnificus (inhibitory zone diameter of ≥15 mm, 100 mcg on disk). The electronic and hydrophobic parameters appeared to hold a conspicuous part in directing the antibacterial properties of the compounds. This study revealed seaweed-associated B. amyloliquefaciens as potential source of antimicrobial polyketides for pharmaceutical applications.

Antioxidative and anti-inflammatory pyranoids and isochromenyl analogues from Corbiculid bivalve clam, Villorita cyprinoides

Bivalve black clam, Villorita cyprinoides is traditional seafood in Southwestern coast of Arabian Sea. In this study, bioactivity-guided purification of ethyl acetate:methanol extract of black clam was carried out. Two irregular meroterpenoids {tetrahydro-3-methoxy-5-((E)-8,12-dimethyloct-8-enyl)-pyran-2-one (1) and dihydro-5-(8-(9,12-dihydro-8-methyl-11-propyl-2H-pyran-8-yl)-ethyl)-furan-2(3H)-one (2)} and two hexahydro-isochromenyl-meroterpenoids (3-4) were identified. The structures were characterized by detailed spectroscopy and their antioxidant/anti-inflammatory potentials were evaluated. Compound 2 registered significantly greater 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability (IC₅₀ <0.65 mg/mL) than other analogues (IC₅₀ ≥0.70 mg/mL). Ferrous ion (Fe²⁺) chelating ability was higher for 1-2 (IC₅₀ ∼0.84 mg/mL) than α-tocopherol (IC₅₀ 0.89 mg/mL). The 5-lipoxygenase inhibitory potential of furano-meroterpenoid analogue, 2 (IC₅₀ 0.76 mg/mL) was greater than other compounds (IC₅₀ >0.90 mg/mL). An optimum hydrophobic-hydrophilic balance of furano-meroterpenoid and lesser steric bulk manifested towards its greater bioactivities compared to other compounds. These anti-inflammatory and antioxidant leads could be used as potential functional food components.

Effects of antioxidative substances from seaweed on quality of refined liver oil of leafscale gulper shark, Centrophorus squamosus during an accelerated stability study

Crude liver oil of leafscale gulper shark, Centrophorus squamosus was clarified by sequential degumming, decolorization and vacuum deodorization. The refined oil was added with ethyl acetate extract of seaweeds and various physiochemical parameters were evaluated in a time-reliant accelerated storage study. Significantly greater induction time was observed for the oil supplemented with Sargassum wightii and Sargassum ilicifolium (>4.5h) than other seaweed extracts and control oil (~1h). Among different seaweeds, the ethylacetate extracts of S. wightii maintained the oxidation indices of the refined oil below the marginal limits after the study period. No significant reduction in C20-22 long chain fatty acids (1.19%) in the refined oil added with S. wightii was apparent, and was comparable with the synthetic antioxidants (1.07-1.08%). Spectroscopic fingerprint analysis of marker compounds responsible to cause rancidity signified the efficacy of S. wightii to arrest the development of undesirable oxidation products in the refined oil during storage. The antioxidant compounds, 15-(but-19-enyl)-hexahydro-13,16-dimethyl-11-oxo-1H-isochromen-8-yl benzoate (1) and 10-(but-13-en-12-yl)-5-((furan-3-yl)propyl)-dihydrofuran-9(3H)-one (2) isolated from S. wightii appeared to play a major role to deter the oxidative degradation of refined oil thereby enhancing the storage stability.

Specialized oxygenated heterocyclics from Villorita cyprinoides with cyclooxygenase-2 and 5-lipoxygenase inhibitory properties

Villorita cyprinoides is traditional seafood in the coastal regions of Arabian Sea. Bioactivity-guided purification of ethyl acetate:methanol extract of V. cyprinoides resulted in the identification of two O-spirocyclic ether derivatives (1-2) along with one O-heterocyclic irregular meroterpenoid (3). The structures and their relative stereochemistries were elucidated through comprehensive spectroscopic experiments. These specialized metabolites were found to exhibit potential antioxidative (IC₅₀<0.70mg/mL) and anti-inflammatory activities against pro-inflammatory inducible 5-lipoxygenase (anti-5-LOX IC₅₀≤0.80mg/mL) and cyclooxygenase-2 (anti-COX-2 IC₅₀<0.75mg/mL) enzymes. Molecular docking simulations were used to describe the interactions of the isolated compounds (ligands) with COX-2 and 5-LOX inflammation model. The permissible hydrophobic-hydrophilic balance and lesser steric bulk of spirocyclic ether derivative (compound 2), along with greater number of hydrogen bonding interactions in the active sites of COX-2 and 5-LOX manifested towards its greater bioactivities compared to other compounds isolated from V. cyprinoides.

Previously undescribed fridooleanenes and oxygenated labdanes from the brown seaweed Sargassum wightii and their protein tyrosine phosphatase-1B inhibitory activity

Previously undescribed fridooleanene triterpenoids 2α-hydroxy-(28,29)-frido-olean-12(13), 21(22)-dien-20-propyl-21-hex-4'(Z)-enoate, 2α-hydroxy-(28,29)-frido-olean-12(13), 21(22)-dien-20-prop-2(E)-en-21-butanoate and oxygenated labdane diterpenoids 2α-hydroxy-8(17), (12E), 14-labdatriene, 3β, 6β, 13α-tri hydroxy 8(17), 12E, 14-labdatriene were purified from the ethyl acetate-methanol and dichloromethane fractions of the air-dried thalli of Sargassum wightii (Sargassaceae), a brown seaweed collected from the Gulf-of-Mannar of Penninsular India. Inhibitory potential of Δ12 oleanenes towards protein tyrosine phosphatase-1B, the critical regulator of insulin-receptor activity were found to be significantly greater (IC50 0.1 × 10-2 and 0.09 × 10-2 mg/mL, respectively) than the standard sodium metavanadate (IC50 0.31 × 10-2 mg/mL). Fridooleanene triterpenoids displayed greater antioxidant activities (IC50DPPH 0.16-0.18 mg/mL) than the commercially available antioxidants, butylated hydroxytoluene and α-tocopherol (IC50DPPH 0.25 and 0.63 mg/mL, respectively). In general, the oxygenated labdane diterpenoids displayed significantly lesser antioxidant and tyrosine phosphatase-1B inhibitory properties than those exhibited by the fridooleanenes. Bioactivities of the titled compounds were primarily determined by the electronic and lipophilic parameters and not by the steric descriptors. Molecular docking simulations and kinetic studies were employed to describe the tyrosine phosphatase-1B inhibitory mechanism. The previously undescribed fridooleanene triterpenoids might be used as potential anti-hyperglycaemic pharmacophore leads to reduce the risk of elevated postprandial glucose levels.

An unprecedented antioxidative isopimarane norditerpenoid from bivalve clam, Paphia malabarica with anti-cyclooxygenase and lipoxygenase potential

CONTEXT

The yellow-foot bivalve clam, Paphia malabarica Chemnitz (Veneridae) is distributed in the southwest coastal regions of India. The ethyl acetate-methanol extract of this species exhibited significant antioxidant and anti-inflammatory activities.

OBJECTIVES

To purify and characterize the bioactive compound from P. malabarica along with in vitro assays.

MATERIALS AND METHODS

The edible portion of P. malabarica was freeze dried (1.20 kg, yield 20.0%) and extracted with ethyl acetate and methanol (1:1 v/v, 500 mL ×3) by sonication (8 h). The antioxidant activity against DPPH/ABTS⁺and anti-inflammatory potential against cyclooxygenase-1,2 (COX-1, 2)/5-lipoxygenase (5-LOX) enzymes were carried out with varying concentrations (0.25-2.00 mg/mL) to determine the IC₅₀ values. The crude extract was chromatographically fractionated and the fraction showing greater potential was further fractionated to yield the pure compound, which was characterized by extensive NMR, IR and mass spectroscopic analyses.

RESULTS AND DISCUSSION

The fractionation of crude extract of P. malabarica was followed by structural characterization of the new rearranged isopimarane derivative, 18 (4 → 14), 19 (4 → 8)-bis-abeo C₁₉ norditerpenoid. The isopimarane derivative displayed comparable antioxidant activity with α-tocopherol (IC₅₀ DPPH scavenging activity ∼0.6 mg/mL), whereas anti-inflammatory (anti-5-LOX) effect of the title compound was significantly greater (IC₅₀ 0.75 mg/mL) than ibuprofen (IC₅₀ 0.93 mg/mL). In addition, the greater selectivity index (anti-COX-1_IC50/anti-COX-2_IC50 0.85) explained the lesser side effects of the isopimarane norditerpenoid than the nonsteroidal anti-inflammatory drug-based therapies.

CONCLUSIONS

The isopimarane derivative isolated from P. malabrica can be a natural substitute to commercial drugs in future.

Antimicrobial polyketide furanoterpenoids from seaweed-associated heterotrophic bacterium Bacillus subtilis MTCC 10403

Brown seaweed Anthophycus longifolius (Turner) Kützing (family Sargassaceae) associated heterotrophic bacterium Bacillus subtilis MTCC 10403 was found to be a potent isolate with broad range of antibacterial activity against important perceptive food pathogens Vibrio parahaemolyticus, V. vulnificus, and Aeromonas hydrophila. This bacterium was positive for polyketide synthetase gene (KC589397), and therefore, was selected to bioprospect specialized metabolites bearing polyketide backbone. Bioactivity-guided chromatographic fractionation of the ethyl acetate extract of the seaweed-associated bacterium segregated four homologous polyketide furanoterpenoids with potential antibacterial activities against clinically important pathogens. The minimum inhibitory concentration (MIC) assay showed that the referral antibiotics tetracycline and ampicillin were active at 25 μg/mL against the test pathogens, whereas the previously undescribed (4E)-methyl 13-((16-(furan-2-yl) ethyl)-octahydro-7-hydroxy-4-((E)-23-methylbut-21-enyl)-2H-chromen-6-yl)-4-methylpent-4-enoate (compound 1) and methyl 3-(hexahydro-9-((E)-3-methylpent-1-enyl)-4H-furo[3,2-g]isochromen-6-yl) propanoate (compound 3) displayed antibacterial activities against the test pathogens at a lesser concentration (MIC < 7 μg/mL). The title compounds were characterized by comprehensive nuclear magnetic resonance and mass spectroscopic experiments. Polyketide synthase catalyzed putative biosynthetic mechanism additionally corroborated the structural ascriptions of the hitherto undescribed furanoterpenoids from seaweed-associated bacterial symbiont. The electronic and hydrophobic parameters appeared to hold a conspicuous part in directing the antibacterial properties of the compounds. Seaweed-associated B. subtilis MTCC 10403 demonstrated to represent a potential source of antimicrobial polyketides for pharmaceutical applications.

Unprecedented antioxidative and anti-inflammatory aryl polyketides from the brown seaweed Sargassum wightii

Previously undescribed aryl polyketide lactones, 4-(8-ethyl-tetrahydro-7-oxo-2H-pyran-5-yl)-propyl-4'-methylbenzoate (compound 1) and methyl-2-(12-oxo-7-phenyl-8-vinyl-1-oxa-4,9-cyclododecadien-3-yl)-acetate (compound 2) were purified from ethyl acetate-methanol fraction of the brown seaweed Sargassum wightii. The structures were proposed based on their NMR and mass spectrometric data. The antioxidative activities of the lactones were significantly greater (P<0.05) (IC50 1,1-diphenyl-2-picrylhydrazyl radical scavenging 0.24-0.32mg/mL) than α-tocopherol (IC50 0.63mg/mL). The title compounds displayed considerably greater 5-lipoxygenase inhibitory activity (IC50 0.56 and 0.29mg/mL, respectively) in conjunction with higher selectivity indices (anti-cycloxygense-1IC50/anti-cycloxygense-2IC50 >1) compared to non-steroidal anti-inflammatory drugs (SIaspirin 0.03, SIibuprofen 0.43). Putative biosynthetic pathway of title polyketide products through polyketide synthase enzyme cascade catalyzed reactions substantiated the structural attributions of the hitherto unreported aryl polyketides. This is the first report of the occurrence and characterization of two rare skeletal types, oxo-2H-pyranyl and oxa-cyclododecadienyl macrolactone featuring the aryl substituent from marine organisms with potential antioxidative and anti-inflammatory activities.

Two rare antioxidant and anti-inflammatory oleanenes from loop root Asiatic mangrove Rhizophora mucronata

Two oleanenes, olean-18(19)-en-3β-yl-(3,6-dimethyl-3E,6Z-dienoate) and (13α)-27-frido-olean-14(15)-en-(17α)-furanyl-3β-ol representing a class of rare natural pentacyclic triterpenoids were isolated from the chloroform extract of Asiatic mangrove, Rhizophora mucronata Lam. (Family: Rhizophoraceae). The furanyl oleanene exhibited significantly greater antioxidative activities (IC₅₀ 0.73-0.76 mg/mL), than prenylated oleanene (IC₅₀ 0.84-0.96 mg/mL) (P < 0.05). No significant differences in anti-5-lipoxygenase activities of these compounds with the synthetic drug ibuprofen was discernable (IC₅₀ 0.8-0.9 mg/mL), whilst furanyl oleanene demonstrated significantly greater anti-cyclooxygenase-2 (IC₅₀ 0.84 mg/mL) and anti-5-lipoxygenase activities (IC₅₀ 0.78 mg/mL) over prenylated oleanene (IC₅₀ > 0.90 mg/mL). These compounds exhibited lesser activity against cyclooxygenase-1 than cyclooxygenase-2 isoform, and therefore, their selectivity indices remained significantly greater (anti-cyclooxygenase-1_IC50/anti-cyclooxygenase-2_IC50 > 1) than the aspirin (0.02) and ibuprofen (0.44). The lipophilic and steric molecular descriptors were found to occupy a prominent role in determining the bioactivities of the compounds. These previously undescribed oleanenes might serve as potential antioxidative and anti-inflammatory lead molecules in medicinal formulations and food industries.

Abstract P1-08-10: Introduction of H1047R oncogenic mutation of PI3K p110alpha subunit in HER2-overexpressing mammary epithelial cells confers a "stem-like" phenotype and acute sensitivity to HSP90 inhibition

The Human Epidermal Growth Factor Receptor 2 (HER2) oncogene is amplified in one-fifth of breast cancers (BC). However, development of resistance against standard anti-HER2 therapies poses a major clinical challenge. Anti-tumor efficacy of HER2-targeting agents depends on inhibition of the downstream phosphatidylinositol-3 kinase (PI3K) signaling cascade. Gain-of-function somatic mutations in the gene encoding the PI3K catalytic subunit p110alpha (PIK3CA), co-expressed in about 40% of HER2+ BC, have been implicated in conferring resistance to HER2 monoclonal antibody herceptin. The single amino acid alteration H1047R within the kinase domain of PIK3CA is one of three hot spot mutations prevalent in BC.

Previously, we demonstrated that introduction of H1047R mutation in HER2-overexpressing MCF10A mammary epithelial cells enhances cellular transformation and decreases herceptin sensitivity by inducing secretion of endogenous ErbB ligand heregulin. However, genetic ablation of HER3, the major co-receptor for HER2 and the solitary receptor for heregulin, was insufficient for complete inhibition of cell growth, indicating the existence of additional mechanism/s responsible for the heightened aggressiveness and decreased drug sensitivity of HER2/H1047RPI3K cells. In the current study, we looked further into the molecular changes within these cells that might be responsible for these phenomena.

When compared with the HER2/WTPI3K cells, the HER2/H1047RPI3K cells revealed a significant increase in CD44high/CD24low/negative populations, common markers of BC stem cells, as well as molecular and phenotypic changes associated with epithelial-to-mesenchymal transition. These observations are in agreement with previously published report on mouse model of HER2/H1047RPI3K BC. Further analyses demonstrated additional stem cell-associated characteristics in HER2/H1047RPI3K cells, such as expression of angiogenic and inflammatory cytokines, ability to induce chemotaxis and invasion, activation of TGFb and NFKb signaling pathways. Connectivity map (CMap) analysis of the gene expression signatures from HER2/H1047RPI3K cells revealed a negative association with those from BC cells treated with 17AAG, an inhibitor of the heat shock protein 90 (HSP90). In line with this, HER2/H1047RPI3K-expressing cells are found to be more sensitive to HSP90 inhibition compared to the pan-ErbB inhibitor lapatinib.

Cancer stem cells are implicated in drug resistance and tumor recurrence. Enrichment of cell population expressing high levels of stem cell markers and stem cell-related features could be one of major mechanisms by which BC cells co-expressing HER2 and H1047RPI3K adapt to anti-HER2 therapeutic agents. Acute dependence on molecular chaperone HSP90 provides a unique, yet practical opportunity to effectively inhibit tumors harboring both molecular alterations, since HSP90 inhibitors have already shown encouraging clinical activity in herceptin-resistant setting.

Citation Format: Surendran S, Bhola N, Arteaga CL, Chakraborty K, Chakrabarty A. Introduction of H1047R oncogenic mutation of PI3K p110alpha subunit in HER2-overexpressing mammary epithelial cells confers a "stem-like" phenotype and acute sensitivity to HSP90 inhibition [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-08-10.

O-heterocyclic derivatives with antibacterial properties from marine bacterium Bacillus subtilis associated with seaweed, Sargassum myriocystum

The brown seaweed, Sargassum myriocystum associated with heterotrophic bacterium, Bacillus subtilis MTCC 10407 (JF834075) exhibited broad-spectra of potent antibacterial activities against pathogenic bacteria Aeromonas hydrophila, Vibrio vulnificus, and Vibrio parahaemolyticus. B. subtilis MTCC 10407 was found to be positive for polyketide synthetase (pks) gene, and therefore, was considered to characterize secondary metabolites bearing polyketide backbone. Using bioassay-guided fractionation, two new antibacterial O-heterocyclic compounds belonging to pyranyl benzoate analogs of polyketide origin, with activity against pathogenic bacteria, have been isolated from the ethyl acetate extract of B. subtilis MTCC 10407. In the present study, the secondary metabolites of B. subtilis MTCC 10407 with potent antibacterial action against bacterial pathogens was recognized to represent the platform of pks-1 gene-encoded products. Two homologous compounds 3 (3-(methoxycarbonyl)-4-(5-(2-ethylbutyl)-5,6-dihydro-3-methyl-2H-pyran-2-yl)-butyl benzoate) and 4 [2-(8-butyl-3-ethyl-3,4,4a,5,6,8a-hexahydro-2H-chromen-6-yl)-ethyl benzoate] also have been isolated from the ethyl acetate extract of host seaweed S. myriocystum. The two compounds isolated from ethyl acetate extract of S. myriocystum with lesser antibacterial properties shared similar structures with the compounds purified from B. subtilis that suggested the ecological and metabolic relationship between these compounds in seaweed-bacterial relationship. Tetrahydropyran-2-one moiety of the tetrahydropyrano-[3,2b]-pyran-2(3H)-one system of 1 might be cleaved by the metabolic pool of seaweeds to afford methyl 3-(dihydro-3-methyl-2H-pyranyl)-propanoate moiety of 3, which was found to have no significant antibacterial activity. It is therefore imperative that the presence of dihydro-methyl-2H-pyran-2-yl propanoate system is essentially required to impart the greater activity. The direct involvement of polarisability (Pl) with the target bioactivity in 2 implied that inductive (field/polar) rather than the steric effect (parachor) appears to be the key factor influencing the induction of antibacterial activity. The present work may have a footprint on the use of novel O-heterocyclic polyketide products from seaweed-associated bacterium for biotechnological, food, and pharmaceutical applications mainly as novel antimicrobial secondary metabolites.

Micronutrient Composition of 35 Food Fishes from India and Their Significance in Human Nutrition

The micronutrients (vitamins and minerals) are required in small amounts but are essential for health, development, and growth. Micronutrient deficiencies, which affect over two billion people around the globe, are the leading cause of many ailments including mental retardation, preventable blindness, and death during childbirth. Fish is an important dietary source of micronutrients and plays important role in human nutrition. In the present investigation, micronutrient composition of 35 food fishes (includes both finfishes and shellfishes) was investigated from varying aquatic habitats. Macrominerals (Na, K, Ca, Mg) and trace elements (Fe, Cu, Zn, Mn, Se) were determined by either atomic absorption spectroscopy (AAS) or inductively coupled plasma mass spectrometry (ICP-MS)/atomic emission spectrometry (ICP-AES). Phosphorus content was determined either spectrophotometrically or by ICP-AES. Fat-soluble vitamins (A, D, E, K) were analyzed by high-performance liquid chromatography (HPLC). The analysis showed that, in general, the marine fishes were rich in sodium and potassium; small indigenous fishes (SIFs) in calcium, iron, and manganese; coldwater fishes in selenium; and the brackishwater fishes in phosphorous. The marine fishes Sardinella longiceps and Epinephelus spp. and the SIFs were rich in all fat-soluble vitamins. All these recommendations were made according to the potential contribution (daily value %) of the species to the recommended daily allowance (RDA). Information on the micronutrients generated would enhance the utility of fish in both community and clinical nutrition.

New sterols with anti-inflammatory potentials against cyclooxygenase-2 and 5-lipoxygenase from Paphia malabarica

Marine bivalves occupy a leading share in the total edible molluscs at the coastline regions of south-eastern Asia, and are found to possess significant nutritional and biological potential. Various in vitro evaluation (antioxidant and anti-inflammatory) guided purification of ethyl acetate-methanol (EtOAc-MeOH) extract of bivalve clam, Paphia malabarica characterised two new sterol derivatives as 23-gem-dimethylcholesta-5-en-3β-ol (1) and (22E)-24¹,24²-methyldihomocholest-5,22-dien-3β-ol (2) collected from the south-west coast of Arabian Sea. Their structures were unambiguously assigned on the basis of 1D, 2D NMR spectroscopy and mass spectrometry. The antioxidant and anti-inflammatory activities of 2 as determined by DPPH/ABTS⁺ radical scavenging and anti-cyclooxygenase-2/5-lipoxygenase assays were significantly greater (IC₅₀ < 1 mg/mL) than 1 (IC₅₀ > 1 mg/mL). Structure-activity relationship analysis revealed that the bioactivities of these compounds were directly proportional to the electronic and lipophilic parameters. This is the first report of the occurrence and characterisation of 23-gem-dimethyl-3β-hydroxy-Δ⁵-cholestane nucleus and C-30 dihomosterol from marine organisms.

Antimicrobial properties of cultivable bacteria associated with seaweeds in the Gulf of Mannar on the southeast coast of India

In this study, 234 bacterial strains were isolated from 7 seaweed species in the Gulf of Mannar on the southeast coast of India. The strains having consistent antimicrobial activity were chosen for further studies, and this constituted about 9.8% of the active strains isolated. Phylogenetic analysis using 16S rDNA sequencing with the help of classical biochemical identification indicated the existence of 2 major phyla, Firmicutes and Proteobacteria. Antimicrobial activity analysis combined with the results of amplifying genes encoding for polyketide synthetase and nonribosomal peptide synthetase showed that seaweed-associated bacteria had broad-spectrum antimicrobial activity. These epibionts might be beneficial to seaweeds by limiting or preventing the development of competing or fouling bacteria. Phylogenetic analysis of ketosynthase (KS) regions with respect to the diverse range of KS domains showed that the KS domains from the candidate isolates were of Type I. The bacterial cultures retained their antimicrobial activities after plasmid curing, which further suggested that the antimicrobial activity of these isolates was not encoded by plasmid, and the genes encoding the antimicrobial product might be present within the genome. Seaweed-associated bacteria with potential antimicrobial activity suggested that the seaweed species are an ideal ecological niche harboring specific bacterial diversity representing a largely underexplored source of antimicrobial secondary metabolites.

First report of two new antioxidative meroterpeno 2H-pyranoids from short-necked yellow-foot clam Paphia malabarica (family: Veneridae) with bioactivity against pro-inflammatory cyclooxygenases and lipoxygenase

Two new meroterpeno 2H-pyranoids were isolated from the EtOAc:MeOH extract of yellow-foot clam Paphia malabarica. The structures of these newly reported compounds were elucidated based on spectroscopic interpretations. This is the first report of biogenic 2H-pyrans bearing decadienyl and allyloxy-(isopentanyl)-cyclohexene skeletons from marine biota. The extended C₁₈ sesquiterpenoid with prenylated irregular farnesene framework was characterised as 2-((E)-deca-1,8-dien-10-yl)-11,12-dihydro-13-propyl-2H-pyran (1). The compound 2, 1'-((10E)-10-(10-(pentan-4-yl)-cyclohex-4-enyl)-allyloxy)-tetrahydro-2',2'-dimethyl-2H-pyran represents the first example of naturally occurring C₂₁ prenylated bisabolene-type meroterpenoid, whereas tetrahydro-2',2'-dimethyl-2H-pyran remains attached at C-2' position of rearranged bisabolene framework formed by allyloxy linkage. The antioxidant activities (DPPH/ABTS⁺) of 1 and 2 were comparable (IC₅₀ < 1.0 mg/mL) with α-tocopherol. In addition, these compounds exhibited greater activity against cyclooxygenase-2 than COX-1, and the selectivity indices were significantly lesser (~1.1). No significant differences in anti-5-lipoxygenase activity of 1 and 2 (IC₅₀ 1.02-1.06 mg/mL) than ibuprofen (IC₅₀ 0.93 mg/mL) indicated the potential anti-inflammatory properties of title compounds.

Characterization of substituted aryl meroterpenoids from red seaweed Hypnea musciformis as potential antioxidants

The ethyl acetate fraction of red seaweed Hypnea musciformis was purified to yield three substituted aryl meroterpenoids, namely, 2-(tetrahydro-5-(4-hydroxyphenyl)-4-pentylfuran-3-yl)-ethyl-4-hydroxybenzoate (1), 2-2-[(4-hydroxybenzoyl)-oxy]-ethyl-4-methoxy-4-2-[(4-methylpentyl)oxy]-3,4-dihydro-2H-6-pyranylbutanoic acid (2) and 3-((5-butyl-3-methyl-5,6-dihydro-2H-pyran-2-yl)-methyl)-4-methoxy-4-oxobutyl benzoate (3). The structures of these compounds, as well as their relative stereochemistries, were confirmed by exhaustive NMR spectroscopic data analyses. Compound 1 exhibited similar 2,2'-diphenylpicrylhydrazyl radical inhibiting and Fe(2+) ion chelating activities (IC50 25.05 and 350.7μM, respectively) as that of commercial antioxidant gallic acid (IC50 32.3 and 646.6μM, respectively), followed by 3 (IC50 231.2 and 667.9μM, respectively), and 2 (IC50 322.4 and 5115.3μM, respectively), in descending order of activities. Structure-activity relationship analysis revealed that the antioxidant activities of these compounds were directly proportional to the steric and hydrophobic parameters. The seaweed derived aryl meroterpenoids might serve as potential lead antioxidative molecules for use in pharmaceutical and food industries.

Production and characterization of refined oils obtained from Indian oil sardine (Sardinella longiceps)

Crude Sardinella longiceps oil was refined in different stages such as degumming, neutralization, bleaching, and deodorization. The efficiency of these processes was evaluated on the basis of free fatty acid (FFA), peroxide (PV), p-anisidine (pAV), total oxidation (TOTOX), thiobarbituric acid reactive species (TBARS) values, Lovibond CIE-L*a*b* color analyses, and (1)H NMR or GC-MS experiments. The utilities of NMR-based proton signal characteristics as new analytical tools to understand the signature peaks and relative abundance of different fatty acids and monitoring the refining process of fish oil have been demonstrated. Phosphoric acid (1%) was found to be an effective degumming reagent to obtain oil with the lowest FFA, PV, pAV, TOTOX, and TBARS values and highest color reduction. Significant reduction in the contents of hydrocarbon functionalities as shown by the decrease in proton integral in the characteristic (1)H NMR region was demonstrated by using 1% H3PO4 during the course of the degumming process. A combination (1.25:3.75%) of activated charcoal and Fuller's earth at 3% concentration for a stirring time of 40 min was found to be effective in bleaching the sardine oil. This study demonstrated that unfavorable odor-causing components, particularly low molecular weight carbonyl compounds, could successfully be removed by the refining process. The alkane-dienals/alkanes, which cause unfavorable fishy odors, were successfully removed by distillation (100 °C) under vacuum with aqueous acetic acid solution (0.25 N) to obtain greater quality of refined sardine oil, a rich source of essential fatty acids and improved oxidative stability. The present study demonstrated that the four-stage refinement process of sardine oil resulted in a significant improvement in quality characteristics and nutritional values, particularly n-3 PUFAs, with improved fish oil characteristics for use in the pharmaceutical and functional food industries.